Weights for fishing lines adapted to be on a float line on which is mounted, at one end, a hook if desired associated with a bait or lure, are known. The weights are generally constituted by a pair of jaws of lead forming a shell of sufficient capacity to enclose a hook and if desired its bait. The jaws, in known sinkers, are generally articulated about themselves and are subjected permanently to the action of a resilient return member which maintains them closed. These jaws moreover comprise manipulating means in the form of a tongue or a handle. These line weights are particularly described in French patents FR-A-2.660.835 and FR-A-2.371.141. These sinkers are particularly cumbersome and often give rise to loss of the lower end of the line because of hooking of the sinker at the bottom of the body of water.